Basic keyword search is great at recall but precision (top 10) gets worse as the number of documents increases. Given the size of the web, basic keyword search tends to perform poorly in terms of relevance. Common Crawl is large enough to see this problem.

I think what OP and several people in this thread actually want is Google search minus synonyms and the ability to specify advanced syntax like AND and NEAR queries. I believe that would go a long way to satisfying someone who says they just want "keyword search".